A large-scale antenna technology is an important technology in the future 5th generation wireless communications system. In a wireless communications network, additional spatial multiplexing gains and diversity gains can be brought by using large-scale antennas at a base station (BS for short) end. For example, multiple antennas at the BS end may be used to implement cancellation of interference between multiple users, and multiple antennas at the BS end may also be used to implement beamforming, so that received signal energy at a user equipment (UE for short) end is improved.
In an existing frequency division duplex (FDD for short) wireless communications system, a general method for obtaining channel state information at the transmitter (CSIT for short) at a BS end is as follows: The BS end first sends a training sequence in a length of T to UE, and the UE receives a channel response sequence obtained after the training sequence passes through a channel, uses a least square method (LS for short) to restore the channel state information (CSI for short) from the channel response sequence, and then feeds back the restored CSI to the BS end by using an uplink feedback link.
However, feedback overheads of UE are high by using an existing CSIT estimation method.